Hi Bin,
On Sat, 5 Oct 2019 at 08:36, Bin Meng <bmeng...@gmail.com> wrote:
>
> Hi Simon,
>
> On Wed, Sep 25, 2019 at 10:58 PM Simon Glass <s...@chromium.org> wrote:
> >
> > Most of the timer-calibration methods are not needed on recent Intel CPUs
> > and just increase code size. Add an option to use the known-good way to
> > get the clock frequency in TPL. Size reduction is about 700 bytes.
> >
> > Signed-off-by: Simon Glass <s...@chromium.org>
> > ---
> >
> > drivers/timer/Kconfig | 29 +++++++++++++++++++----------
> > drivers/timer/tsc_timer.c | 7 +++++--
> > 2 files changed, 24 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
> > index 5f4bc6edb67..90bc8ec7c53 100644
> > --- a/drivers/timer/Kconfig
> > +++ b/drivers/timer/Kconfig
> > @@ -117,16 +117,6 @@ config RENESAS_OSTM_TIMER
> > Enables support for the Renesas OSTM Timer driver.
> > This timer is present on Renesas RZ/A1 R7S72100 SoCs.
> >
> > -config X86_TSC_TIMER_EARLY_FREQ
> > - int "x86 TSC timer frequency in MHz when used as the early timer"
> > - depends on X86_TSC_TIMER
> > - default 1000
> > - help
> > - Sets the estimated CPU frequency in MHz when TSC is used as the
> > - early timer and the frequency can neither be calibrated via some
> > - hardware ways, nor got from device tree at the time when device
> > - tree is not available yet.
> > -
> > config OMAP_TIMER
> > bool "Omap timer support"
> > depends on TIMER
> > @@ -174,6 +164,25 @@ config X86_TSC_TIMER
> > help
> > Select this to enable Time-Stamp Counter (TSC) timer for x86.
> >
> > +config X86_TSC_TIMER_EARLY_FREQ
> > + int "x86 TSC timer frequency in MHz when used as the early timer"
> > + depends on X86_TSC_TIMER
> > + default 1000
> > + help
> > + Sets the estimated CPU frequency in MHz when TSC is used as the
> > + early timer and the frequency can neither be calibrated via some
> > + hardware ways, nor got from device tree at the time when device
> > + tree is not available yet.
> > +
> > +config TPL_X86_TSC_TIMER_NATIVE
> > + bool "x86 TSC timer uses native calibration"
> > + depends on TPL && X86_TSC_TIMER
> > + help
> > + Selects native timer calibration for TPL and don't include the
> > other
> > + methods in the code. This helps to reduce code size in TPL and
> > works
> > + on fairly modern Intel chips. Code-size reductions is about 700
> > + bytes.
> > +
> > config MTK_TIMER
> > bool "MediaTek timer support"
> > depends on TIMER
> > diff --git a/drivers/timer/tsc_timer.c b/drivers/timer/tsc_timer.c
> > index 919caba8a14..9630036bc7f 100644
> > --- a/drivers/timer/tsc_timer.c
> > +++ b/drivers/timer/tsc_timer.c
> > @@ -49,8 +49,7 @@ static unsigned long native_calibrate_tsc(void)
> > return 0;
> >
> > crystal_freq = tsc_info.ecx / 1000;
> > -
> > - if (!crystal_freq) {
> > + if (!CONFIG_IS_ENABLED(X86_TSC_TIMER_NATIVE) && !crystal_freq) {
> > switch (gd->arch.x86_model) {
> > case INTEL_FAM6_SKYLAKE_MOBILE:
> > case INTEL_FAM6_SKYLAKE_DESKTOP:
> > @@ -405,6 +404,10 @@ static void tsc_timer_ensure_setup(bool early)
> > if (fast_calibrate)
> > goto done;
> >
> > + /* Reduce code size by dropping other methods */
> > + if (CONFIG_IS_ENABLED(X86_TSC_TIMER_NATIVE))
> > + panic("no timer");
> > +
>
> I don't get it. How could this reduce the code size? I don't see any
> #ifdefs around the other methods we want to drop?
The compiler sees that CONFIG_IS_ENABLED(..) is 1, and leaves out the
code that follows it.
>
> > fast_calibrate = cpu_mhz_from_cpuid();
> > if (fast_calibrate)
> > goto done;
> > --
>
> Regards,
> Bin
Regards,
Simon
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